Papers by Keyword: Surface Migration

Abstract: Surface migration of additives in a surfactant-loaded natural rubber vulcanizate is investigated as function of ingredient loading. Rubber sheets are compounded according to an L12 orthogonal array using Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Migration experiments are performed by placing the rubber sheets in a natural convection oven at 50°C for 32 days. Weight loss due to removal of migrated additives from surface of rubber sheets is monitored with time. The maximum amount and estimated rate of additive migration are determined from weight loss curves. Attenuated total reflection – Fourier transform infrared (ATR-FTIR) spectroscopy and optical microscopy are used to characterize the chemical structure and surface morphology of rubber sheets during additive migration. Mean effects and analysis of variance (ANOVA) show that high loadings of used oil, paraffin wax, stearic acid, glycerol monostearate (GMS), and cocamide diethanolamide (Coca DEA) increase the amount of maximum migration and migration rate of additives. On the other hand, high loadings of mercaptobenzothiazole (MBT), diphenylguanidine (DPG), mercaptobenzothiazole disulfide (MBTS), sulfur, and zinc oxide (ZnO) decrease the maximum amount of additive migration and migration rate. Used oil has the highest effect on these responses, while sulfur and the accelerators have the least effect. By comparing the of ATR-FTIR spectra of cleaned and migrated rubber surfaces, almost all soluble additives are identified to have migrated to the rubber surface.

Abstract: Many cracks can occur in heavy forging as a result of inherent defects of heavy ingot and forging process. According to the results of current research, internal crack of metallic material can heal under high temperature. In order to get to the bottom of internal crack healing in heavy forgings, some 45 steel samples containing internal crack were normalized at higher temperature than normal. The phenomena show that new ferrite grains nucleate and grow up on the crack surfaces during the crack healing, and the ferrite grains nucleation is universal but selective on crack surfaces. The relationship of atom diffusion and ferrite grain nucleation and their actions on crack surface migration will be discussed and expounded, and that proves that ferrite grain nucleation and growth will accelerate crack healing.

Abstract: Scanning tunneling microscopy (STM) proved the existence of quasi-compounds on solid surfaces. A typical example is (-Ag-O-) or (-Cu-O-) chains grown on Ag(110) or Cu(110) surface by exposing to O2. The (-Ag-O-) chains on a Ag(110) reacts with Cu atoms to form a new quasi-compound of (-Cu-O-) chains on the Ag(110) surface. The (-Cu-O-) on the Ag(110) readily decomposes at ca. 570ºK to form Cu6 dots, and a reversible reaction of (Cu2)3 + O2. ↔ (-Cu-O-) takes place by exposing to O2. Deposited Zn, Sn and Ag atoms on a Si(111)-7x7 surface stabilize by forming Zn3, Sn2 and Sn, and Ag in a half unit cell. Layer-by-layer growth of Zn3 clusters occurs in a half unit cell, which results in the growth of a semi-conductive honeycomb layer of Zn3 clusters on the Si(111)-7x7 surface. By prohibiting hopping migration of Ag atoms on the Si(111)-7x7 surface by the adsorption of C2H5OH, nano-size Ag dots grow layer-by-layer in a limited mold spacing. The band gap of Ag-dots becomes narrower and narrower and becomes metallic at higher than 6 layers.